In many situations, it can be desirable to image the interior of opaque objects. By way of example but not limitation, in the medical field, it can be desirable to image the interior of a patient's body so as to allow viewing of internal body structures without physically penetrating the skin.
Computerized Tomography (CT) has emerged as a key imaging modality in the medical field. CT imaging systems generally operate by directing X-rays into the body from a variety of positions, detecting the X-rays passing through the body, and then processing the detected X-rays so as to build a three-dimensional (3D) data set and a 3D computer model of the patient's anatomy. The 3D data set and 3D computer model can then be visualized so as to provide images (e.g., slice images, 3D computer images, etc.) of the patient's anatomy.
By way of example but not limitation, and looking now at FIGS. 1 and 2, there is shown a mobile CT imaging system 5 of the sort disclosed in U.S. Pat. No. 7,397,895, issued Jul. 8, 2008 to Eric M. Bailey et al. for MOBILE COMPUTERIZED TOMOGRAPHY (CT) IMAGING SYSTEM WITH CORDLESS AND WIRELESS CAPABILITIES, which patent is hereby incorporated herein by reference. Mobile CT imaging system 5 generally comprises a torus 10 which is supported by a base 15. Torus 10 and base 15 together comprise a frame for mobile CT imaging system 5. A center opening 20 is formed in torus 10. Center opening 20 receives the patient anatomy which is to be scanned.
Looking next at FIG. 3, torus 10 generally comprises an X-ray tube assembly 25, an X-ray detector assembly 30, and a rotating drum assembly 35. X-ray tube assembly 25 and X-ray detector assembly 30 are mounted to rotating drum assembly 35 in diametrically-opposing relation, such that an X-ray beam 40 (generated by X-ray tube assembly 25 and detected by X-ray detector assembly 30) is passed through the patient anatomy disposed in center opening 20. Furthermore, since X-ray tube assembly 25 and X-ray detector assembly 30 are mounted on rotating drum assembly 35 so that they are rotated concentrically about center opening 20, X-ray beam 40 will be passed through the patient's anatomy along a full range of radial positions, so as to enable mobile CT imaging system 5 to create a “slice” image of the anatomy penetrated by the X-ray beam. Furthermore, by moving mobile CT imaging system 5 relative to the patient during scanning, a series of slice images can be acquired, and thereafter appropriately processed, so as to create a 3D computer model of the scanned anatomy.
The various electronic hardware and software for controlling the operation of X-ray tube assembly 25, X-ray detector assembly 30, and rotating drum assembly 35, as well as for processing the acquired scan data so as to generate the desired slice images and 3D computer model, may be of the sort well known in the art and may be located in torus 10 and/or base 15.
Still looking now at FIG. 3, base 15 comprises a transport assembly 50 for moving mobile CT imaging system 5 relative to the patient. More particularly, as disclosed in the aforementioned U.S. Pat. No. 7,397,895, transport assembly 50 preferably comprises (i) a gross movement mechanism 55 for moving mobile CT imaging system 5 relatively quickly across room distances, so that the mobile CT imaging system can be quickly and easily brought to the “bedside” of the patient, and (ii) a fine movement mechanism 60 for moving the mobile CT imaging system precisely, relative to the patient, during scanning, so that the patient can be scanned at their bedside, without being moved. As discussed in U.S. Pat. No. 7,397,895, gross movement mechanism 55 preferably comprises a plurality of free-rolling casters, and fine movement mechanism 60 preferably comprises a plurality of centipede belt drives (which can be configured for either stepped or continuous motion, whereby to provide either stepped or continuous scanning). Hydraulic apparatus 65 permits either gross movement mechanism 55 or fine movement mechanism 60 to be engaged with the floor, whereby to facilitate appropriate movement of mobile CT imaging system 5.
Looking next at FIGS. 4 and 5, there is shown another mobile CT imaging system 105 of the sort disclosed in U.S. patent application Ser. No. 13/304,006, filed Nov. 23, 2011 by Eric M. Bailey et al. for ANATOMICAL IMAGING SYSTEM WITH CENTIPEDE SCANNING DRIVE, BOTTOM NOTCH TO ACCOMMODATE BASE OF PATIENT SUPPORT, AND MOTORIZED DRIVE FOR TRANSPORTING THE SYSTEM BETWEEN SCANNING LOCATIONS, which patent application is hereby incorporated herein by reference. Mobile CT imaging system 105 is generally similar to mobile CT imaging system 5 disclosed above, except that (i) mobile CT imaging system 105 is generally “scaled up” in size relative to mobile CT imaging system 5, (ii) a bottom notch 170 is provided in skirt 175 of mobile CT imaging system 105, and (iii) the casters of gross movement mechanism 55 of mobile CT imaging system 5 may be replaced by a pair of drive wheels 180A, 180B and a pair of casters 185A, 185B, and each of the centipede belt drives of fine movement mechanism 60 of mobile CT imaging system 5 may be replaced by a pair of parallel belt drives 190A, 190B disposed in side-by-side relation. Additional differences between mobile CT imaging system 105 of FIGS. 4 and 5 and mobile CT imaging system 5 of FIGS. 1-3 are disclosed in the aforementioned U.S. patent application Ser. No. 13/304,006.
For the purposes of the present invention, it is generally immaterial whether the present invention is used in conjunction with the aforementioned mobile CT imaging system 5, the aforementioned mobile CT imaging system 105 or another CT imaging system (e.g., a fixed position CT imaging system).
With all CT imaging systems (i.e., with the aforementioned mobile CT imaging system 5, the aforementioned mobile CT imaging system 105, or another CT imaging system such as a fixed position CT imaging system), it is generally necessary to collimate the X-ray beam emitted by the X-ray tube assembly before the X-ray beam passes through the body. More particularly, X-ray tube assemblies generally emit their X-rays in a broad, relatively unfocused pattern, and the anatomy is imaged in a slice fashion, so it is generally desirable to restrict the X-rays reaching the patient to only those X-rays which are actually used for the slices being imaged, and to block the remaining X-rays emitted by the X-ray tube assemblies. This is typically done with a collimator, which is essentially an X-ray shield having a slit formed therein, which is interposed between the X-ray tube assembly and the patient. In this way, the slit permits the “useful” X-rays (i.e., those being used for the slices being imaged) to reach the patient, while the body of the collimator blocks the remainder of the X-rays emitted by the X-ray tube assembly.
In addition to the foregoing, with “modern” CT imaging systems, it is possible to conduct multi-slice scanning of a patient by using a collimator having a slit wide enough to provide an X-ray beam which simultaneously encompasses multiple scan slices. In general, scanning with a wider X-ray beam (i.e., a higher slice count) yields faster scanning of a patient than scanning with a narrower X-ray beam (i.e., a lower slice count), but this is generally at the expense of subjecting the patient to a higher X-ray dose. For this reason, in some situations it may be desirable to make a high slice scan (e.g., a 32 slice scan) of a patient, whereas in other circumstances it may be desirable to make a low slice scan (e.g., an 8 slice scan) of a patient.
Since the width of the X-ray beam is determined by the width of the slit in the collimator, varying the slice count of the scan requires the use of a plurality of collimator slits each having different widths.
Thus there is a need for a fast, simple and reliable way to change collimator slits when the slice count of the scan is to be changed.